Billy Twelvetrees has been called up to the British & Irish Lions squad as injury cover, the Rugby Football Union has announced.

The Gloucester No. 12 will leave England's tour of Argentina for Australia on Wednesday, as Lions head coach Warren Gatland sweats over the fitness of fly-halves Owen Farrell and Jonathan Sexton.

Twelvetrees, who can play centre or fly-half, won his fifth England cap in Saturday's 32-3 victory over the Pumas, scoring a try to cement a positive performance in Salta.

Following the comprehensive 64-0 victory over Combined Country XV,the Lions face New South Wales Waratahs on Saturday and the ACT Brumbies on Tuesday, before the first test with Australia.

With a heavy schedule in mind,Gatland issued that injury call-ups are more than expected when it comes to touring.

"The nature of a Lions tour means that there will inevitably be knocks which take time to recover from," Gatland said.

"The whole squad have worked hard but a lot of the backs have doubled up over the last two games, either starting or from the bench.

"Billy played well in the first Test [against Argentina] for England and he provides that versatility to cover a variety of positions."

England coach Stuart Lancaster, who was set to name Twelvetrees in the line up for the second test with Argentina on Saturday, was quick to praise the 24-year-old's contribution.

"All the England players and management are delighted for Billy to get this great opportunity," Lancaster said.

"He's played well for England this year, underlined that form with his display against Argentina at the weekend and goes with our full support and blessing."

Twelvetrees is the second England player to be pulled away from the tour of Argentina, following Alex Corbisiero's call-up on Wednesday.